Hi,
I know how you feel you look at all these websites and find conflicting stories! Your passport has to be valid for the entire stay. Is your passport due to expire soon? if it expires within 6 months and you have enough time to renew it, then I would say to do that just in case.
But I can talk from experience on this one with passports as I have just spent 3 days in Tunis getting my passport sorted out at the police station for a very long overstay

what I have learnt do not worry too much as Tunisia really is not as strict as many countries (the exact words from the police officer!). When you arrive in Tunis, you will be required to fill in a little visa for your stay depending on how long you intend to visit for. The maximum stay in Tunisia is for 3 months.